Process for retarding the ripening of fruit



United States Patent 3,062,659 PROCESS FOR RETARDING TIE RIPENING 0F FRUlT Archibald M. Hyson, Newark, and Maurice R. Stahler, Jr., Wilmington, DeL, assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed July 6, 1960, Ser. No. 40,998 7 Claims. (61. 99-103) This invention relates to a :process for treating fruits and vegetables with formate esters. This invention also relates to novel products incorporating formate esters for release in the treatment of these fruits and vegetables.

By the term fruit is meant citrus fruits of all types, as well as fruit containing pits, such as peaches, avocados, plums, and mangoes, and fruit containing smaller seeds, such as apples, pears, bananas, grapes, and toma toes.

By the term vegetables is meant any of the edible tubers such as potatoes, carrots, beets, turnips, and the like. The term is also intended to encompass such things as beans and peas, and also such stalk plants as celery, rhubarb, and asparagus.

A source of economic loss to the fruit and vegetable grower arises from the necessity of having to pick certain fruits and vegetables such as citrus fruits, bananas, peppers, and the like while they are still green. They are picked in this condition so that they may reach the consumer before over-ripening occurs. Since these fruits and vegetables must thus be harvested before the maximum weight gain occurs, there is considerable economic loss to the grower. It should also be noted that fruits and vegetables picked before they are completely ripe lose palatability.

Sprouting of tubers in storage is also a problem because of the weight loss involved. Compositions have been developed for dusting tubers prior to storage to prevent sprouting, but these have not been completely satisfactory.

It is an objected of this invention to provide a process which delays the ripening of fruits and vegetables so that they may be picked and shipped at a later stage of ripening, and also to retard the sprouting of tubers while in storage.

Another object is to provide thin films, sheets, layers, and the like, which can be supported in a laminate or coated on a surface, or can be self-supporting, and can be made of such materials as paper, natural or synthetic resins and the like, which films, sheets, or layers have incorporated therein a small amount of at least one of the formate esters described below. These can be used in the wrapping or packaging of the fruits and vegetables to provide a gradual release source of the formate ester.

Other objects and advantages of the invention will appear hereinafter.

We have discovered that the volatile esters of formic acid, especially alkyl formates, retard the ripening processes of fruits and vegetables and also retard sprouting of tubers. This is accomplished by maintaining them in contact with the vapor of said ester. The preferred quantity of ester employed is from 0.0001% to 5.0% of the weight of the fruit. The ripening and sprouting processes will be significantly retarded while this contact is maintained, and ripening or sprouting will proceed normally when the fruits and vegetables are removed from contact with the formate ester vapors.

The formate esters that can be used according to the present invention are the volatile fo-rmate esters including straight chain alkyl esters and also those containing branching or cyclo aliphatic groups and/ or unsaturation in the alcohol moeity of the ester. Examples of these "icevarious types are methyl formate, ethyl form-ate, propyl formate, butyl formate, amyl formate, heXyl formate, heptyl formate, octyl formate, nonyl formate, decyl formate, undecyl formate, dodecyl formate, tridecyl formate, and tetradecyl formate. All position isomers of these formates can also be used. In addition, Z-ethylhexyl formate, isooctyl formate, allyl formate, crotyl formate,

and cyclohexyl formate can be used.

The volatile formates which can be employed in the practice of this invention are preferably alkyl formates having from 1 to 14 carbon atoms in the alkyl group as enumerated above. Particular advantages are obtained in some uses and especially in the film and paper products of this invention by the use of higher alkyl formates of from 8 to 14 carbon atoms.

This invention can be practiced in a number of ways as long as the vapors of the forrnate ester effect contact with the fruit being treated. The longer the contact, of course, the longer the period of effective delay of ripening and inhibition of sprouting.

It will be readily understood, therefore, that the process of this invention in one embodiment is preferably carried out within a confined or enclosed space, area, or container. Anything will serve that acts to present some barrier to the rapid dissipation of the vapors of the volatile ester. For example, the barrier or closure can conveniently be a plastic or paper covering or Wrapper, a

plastic, paper, or cardboard sheet under and/ or over or otherwise partially or completely around one or a number of the fruit or vegetable, as covering a a crate. The closed space can consist of a storage room, refrigerated compartment, warehouse, freight car, etc.

vThe formate esters can be used in concentrated form without adjuvants simply by placing a vessel of the liqold in the same area as the fruit or vegetable.

Mixtures of formates can, of course, be used in this invention and in particular mixtures containing lower alkyl together with higher alkyl formates offer special advantages.

In another embodiment, the esters can be incorporated in formulations such as emulsions, suspensions, solutions, or the like, which can be used to treat the fruit or vegetable by a dip or spray application. These formulations can also be applied to the sheets, films, papers, absorbent papers, etc., which in turn are placed in close proximity to the fruit or vegetable during storage or shipment.

These formulations can be used hot or cold and can con-.

compositions can be used according to procedures Well known in the art.

In a particularly preferred aspect, the volatile formate ester constitutes an essential component of a stratum or the like. For example, wrapping or absorbent paper can be impregnated with the ester by simply dipping the paper into the liquid ester, followed by drying. Suificient ester is retained thereby within the paper to volatilize gradually under use conditions to release the formate ester vapors over a period of time. This paper can be used to wrap the fruit or vegetable, or can be inserted as a sheet between layers of fruit or vegetables in a packing container. In another article, the ester can be admixed with a vaporpermeable resinous material which is then subsequently formed into a sheet or film. Suitable resinous materials include those prepared from polyolefins such as polyethylene, polypropylene, and the like, polyvinyl chloride, etc. Regenerated cellulose film can also be used. The films can be formed by casting, extrusion, or other conventional basket or lining techniques. The films, like the paper, or like similar articles or coated surfaces, are used as described above. The articles can incorporate the ester in an amount from additive. The degree of ripeness was noted after 2 and 3 days. The results after storage at 75 F. are given below:

0.2% to 50% and higher, based on the total weight, de- Percent of Ripening Progress, pending on the type of film or material and the method 5 T t C d 001516115 Test d Days and duration of the intended use. From 0.5% to 20% as ompoun S viifitiffid is preferred. 0 2 3 The invention will be further clarified by the following illustrative examples. ggggg O 06 3 g g Example 1 i ililiiill%lhil%.j ji: 8:? 9i 5 Z 3 Bananas of the Gros Michel variety were obtained in th grass green ta f th t t Thg t t ha b r Color codez2=slightly yellow or very light green; 3=yellow or very pale green; 4=dead ripe. consisted of desiccators, in each of which were placed green bananas and a small amount of formate ester. The It is pp lhatfmer 3 y the Control Peaches had desiccator vent remained open but was covered by cloth F to an Undeslrable degree- The treated P gauze. The degree of ripeness of the bananas was noted on the other hand: proceeded further than Yellow at the end of 6, 7 8, 9 and 10 days. The results are or very pale green stage, and in the case of tetradecyl summarized in the f ll i table; formate, no ripening was observed at all.

Similar results were obtained by using the formates Percent Rimming Progress, Days listed in col. 2, lines 1 to 8, 1n the same concentrations as a of Test in this example. 'lest Compound cglon-g lgolrrrliyi Example 4 g gg 0 6 7 8 9 1O Potatoes were placed in desiccators containing (1) decyl formate; (2) lauryl formate; (3) tetradecyl formate; Control 3 3 4 4 4 and (4) no additive. Results after days storage at Methyl formate 0.1 0 2 2 2 2 2 2 75 F, are shown below: .Decylformate- 0.5 3 7 2 2 2 2 2 2 Laurylformate 0.5 0 6 2 2 2 2 2 2 Tetradccyl formate 0.5 0 3 2 2 2 3 3 3 Wt f Percent 30 Sprouts Reduction "Color code: 2=light green; 3=yellowlsh green; 4=ye1low with traces rlest Compound ffggf of green. Control From the above it will be seen that the control bananas which were not treated with the formate ester 'vapors Control 10.3 ripened to a yellow stage in 8 days, whereas bananas Egggfggggg g2 treated with formate esters remained in their original light etradecyl for ate 2- 9 71 green condition for up to 10 days in the case of methyl formate, decyl formate, and lauryl formate. In the case Th d t h h sprouting of potatoes can b of tetradecyl formate, the bananas progressed no further duced a much as 70 80% by treatment with formate in the ripening process than a yellowish-green stage after 40 ester vapors. Similar results were obtained by using the 10 days. Similar results were obtained by using the forformates listed in column 2, lines 1 to 8. mates listed in col. 2, lines 1 to 8. Example 5 Example 2 Carrots were placed in each of two polyethylene bags. Green tomatoes were placed in each of two desiccators One contained no additive and the other contained 5 maintained at a temperature of 75 F. In one desiccator drops of methyl formate. Both bags were sealed and, was placed 0.5 g. of lauryl formate. The second was after four days storage at 75 F., the control carrots had maintained as the control. The ripeness of the tomatoes begun to sprout. No sprouts were evident after seven was noted after 2, 3, 4, 5, 7, and 11 days. The results days on those treated with methyl formate. follow: This application is a continuation-in-part of my co- Percent Ripening Progress, Days Test Compounds C0ncen., of Test g. Compound Volatilized 1 2 3 4 5 7 11 Control *11123 12334 33445 33455 44455 45555 55555 Lauryl formate 0.5 0.0 11123 11233 22344 22344 22344 23455 33455 Color code: 1=green; 2=light green; 3=blush of pink; 4=pink; 5=red.

Example 3 Both white and yellow peaches in a firm condition were placed in desiccators containing (1) lauryl formate; (2)

tetradecyl formate; (3) cyclohexyl formate; and (4) no pending application Serial No. 852,613, filed November 13, 1959, as a continuation-in part of copending application Serial No. 832,907, filed August 11, 1959.

The invention claimed is:

1. A process for retarding the ripening of fresh fruit and vegetables and the sprouting of tubers, said process comprising maintaining said fruit, vegetables and tubers in contact with from 0.0001 to 5%, by weight, of a volatile formate ester.

2. A process for retarding the ripening of fresh fruit and vegetables and the sprouting of tubers, said process comprising maintaining said fruit, vegetables and tubers in contact with from 0.0001% to 5%, by weight, of an alkyl formate having form 1 to 14 carbon atoms in the alkyl group.

3. A process for retarding the ripening of fresh fruit and vegetables and the sprouting of tubers, said process comprising maintaining said fruit, vegetables and tubers in contact with from 0.0001% to 5%, by weight, of methyl formate.

4. A process for retarding the ripening of fresh fruit and vegetables and the sprouting of tubers, said process comprising maintaining said fruit, vegetables and tubers in contact with from 0.0001% to 5%, by Weight, of ethyl formate.

5. A process for retarding the ripening of fresh fruit and vegetables and the sprouting of tubers, said process comprising maintaining said fruit, vegetables and tubers in contact with from 0.000 1% to 5 by weight, of N- propyl formate.

6. A process for retarding the ripening of fresh fruit and vegetables and the sprouting of tubers, said process comprising maintaining said fruit, vegetables and tubers in contact with from 0.0001% to 5%, by weight, of

, isoamyl for-mate.

6 7. A process for retarding the ripening of fresh fruit and vegetables and the sprouting of tubers, said process comprising maintaining said fruit, vegetables and tubers in contact with from 0.0001% to 5%, by weight, of lauryl fo-rmate.

References Cited in the file of this patent UNITED STATES PATENTS 2,022,139 Meder Nov. 26, 1935 2,511,987 Mrak June 20, 1950 FOREIGN PATENTS r 349,561 Great Britain May 21, 1931 517,079 Great Britain J an. 19, 1940 18,731 Australia Sept. 5, 1935 OTHER REFERENCES Uses and Applications of Chemicals and Related Compounds, vol. II, Gregory, 1944, pages 135 and 2 14. 

1. A PROCESS FOR RETARDING THE RIPENING OF FRESH FRUIT AND VEGETABLES AND THE SPROUTING OF TUBERS, SAID PROCESS COMPRISING MAINTAINING SAID FRUIT, VEGETABLES AND TUBERS IN CONTACT WITH FROM 0.0001% TO 5%, BY WEIGHT, OF A VOLATILE FORMATE ESTER. 